Helicopters are known comprising a fuselage; a main rotor mounted on top of a central portion of the fuselage; and an antitorque tail rotor for counteracting the torque transmitted by the main rotor to the fuselage.
So-called teetering or see-saw antitorque tail rotors are also known, which substantially comprise a drive shaft rotating about a first axis of rotation crosswise to a second axis of rotation of the main rotor; a hub connected functionally to the drive shaft in angularly integral manner about the first axis, and free to oscillate about the drive shaft about a third axis perpendicular to the first axis; and a number of blades projecting from the hub on opposite sides of the drive shaft.
More specifically, the blades are angularly integral with the hub about the third axis, can rotate about the hub about respective fourth axes crosswise to the first and third axis, and extend longitudinally along the respective fourth axes.
The hub thus rotates the blades about the first axis, and allows the blades to rotate, by external control, about the respective fourth axes to adjust the respective angles of attack with respect to the airflow. The hub also allows the blades to oscillate integrally with one another about the third axis to “flap” the blades.
Known see-saw rotors also comprise supporting means for supporting the blades with respect to the hub, and which, more specifically, allow the blades to rotate about the hub along the respective fourth axes.
See-saw rotors are particularly advantageous for helicopters, by comprising few component parts.
A need is felt within the industry for see-saw antitorque tail rotors designed to minimize wear and so ensure a high degree of dependability.
A need is also felt within the industry to reduce transmission to the hub, and hence to the fuselage, of vibration and noise generated by rotation of the blades, at least over predetermined frequency ranges.